Evening star. [volume] (Washington, D.C.) 1854-1972, 1887-09-17
WHY A BASE BALL CURVES.
The Rotation Of a Billiard Rail. q
Base Ball, and y Cannon ball.

A baseball pitcher causes the bali he pitches to
curve on the same principle that billiard player
gives q ball "English." This principle is that
they both cause the greatest friction on the ball
to be on the side they desire repeed. For instance
il billiard players stationed at the middle OF one
end OF billiard table, and desires to cause ball
situated Immediately in front OF him to strike one
Of the side rails midway the table, and then glance
directly across to the other side rail- he will strike
the ball SO that 1t will rotate toward him, with
reference to the rail 1t Is first to strike This rota-
ton Will greatly increase the friction OF the ball
against the rail and cause 1t, when leaving the
rail-, TO take direction much nearer the player
than II he should strike the ball fairly and cause
no rotations. II, when the ball SO rotated should
strike the side rail- IL were Immediately thereupon
to be transfixed by an tmmOvabie perpendicular
axle, its tendency would be to roll the side OF the
table along in the direction Of its ro!aton but as
ball tends to move In direction opposite that in
which 1t would cause the table to go 4 the ball
when the baseball pitcher wishes to make the
ball curve he causes it rotate SO that the fric-
ton against the air win be greatest on the side
II he desires TO make 1t curve to the
right with reference to himselD, he will
cause It to rotate from right to left SO that the
point OF the greatest friction will be on the left
SIDE The rationale of this is that the left side Of
the ball is moving against the air in front OF and
rapidly in the contrary direction. The tendency
OF the ffst-described motion is to compact the air
In front OF the left side and force the ball over to
the right, while the tendency OF the motion Of the
left side IL to reduce the atmospheric pressure on
that side. Hence the pitchers capacity to vary
the directions Of his curves is only limited by his
ability to vary the direction OF the axis Of rota-
tien OF the ball. It may not be known to all the
readers of THE STAR that the phenomenon OF curves
by spheres rotaJOry In direction across their
line OF flight led to the invention OF riding In fire
arms. The flight OF smooth bore spherical shot,
especially In cannon, where the difference In the
size OF the ball and tnat OF the bore OF the gun was
material, was sufficiently eccentric to make artil.
lerists desire something fnsuring more accuracy.
II round-Shot In leaving the gun touched one
side OF the bore near the muzzle with sufTicient
force to give the ball rotary motion, it curved
the flight OF the ball, and as there was no means
OF knowing which way 1t would curve no depend
ence could be placed on 1t for accuracy. This de.
feet was substantially overcome by the principle
OF rtfing, which, by means OF spiral groves In the
bore OF lhe gun, causes the projectile TO revove
direction az right angles to the line OF flight and
secures uniform air pressure on the sides and
front OF the pro1ectfle and Theoretically accuracy
It Is probable that those who applied the riaed
system to firearms were not its inventors. The
writer hos seen Indian arrow heads beveled in
such way that led to the inference that theii
form was intended to contribute rotary motion
to the SHAFT, with the object OF obtaining some OF
the effects OF accuracy and range that rotation
gives to rifed prOjectiiea